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Increasing ex situ conservation efforts in California

Introduction

The California Floristic Province (CFP) is one of the most botanically diverse and threatened regions in North America. The CFP, defined as the Mediterranean climatic region along the Pacific coast of the United States and Baja Peninsula of Mexico, is ranked as a global biodiversity hotspot (Myers et al., 2000). Compared to many other parts of the world, large scale human development and landscape conversions to the CFP are relatively recent. In 1850, the United States census recorded fewer than 100,000 residents in the U.S. state of California; today, the human population in California is approaching 40 million (U.S. Census 2014). This rapid influx of people has had a tremendous negative impact on the region’s biodiversity. Many wildlands and the unique species contained within them have been converted to residential, agricultural and industrial landscapes. In the face of this pressure, extensive efforts to protect the wild landscapes and natural resources of California have been mounted. A network of federal, state and other land conservation jurisdictions manage roughly 45% of the state’s lands with varying degrees of protection from development (Orman and Dreger 2014). The fight to protect land and in situ habitat is ongoing and in need of greater biological study; many lands which are considered protected still face threats to their biodiversity.

Development of ex situ collections

Some of the earliest plant specimens collected by a western botanist in California come from the Scottish explorer, David Douglas, who made the treacherous journey to the West Coast in the early 1830s and collected many plant species that were new to science at that time. As the United States expanded its borders into the western frontier during the 19th Century, scientists in turn enriched their knowledge of its biodiversity. By the early 1900s, herbaria and scientific institutions were established in California, and the unique plants of the region were being grown in botanic gardens both locally and around the world.

These ongoing plant collections have organically led to the existence of substantial ex situ living collections of the California flora. More recently, in response to declines of many California plant species due to loss of wildlands and their degradation through such factors as invasive species proliferation and climate change, the building of well-documented and genetically diverse wild germplasm collections of the rarest plants has been a conservation priority. A number of organizations maintain germplasm of California native plants. Rancho Santa Ana Botanic Garden (RSABG), located in the city of Claremont in eastern Los Angeles County, maintains one of the largest collections of native California seeds.

Currently, the RSABG seed bank contains more than 4,600 seed accessions representing over 1,900 taxa. Seeds are maintained at low humidity in -23°C freezers. The geographic scope of the RSABG collection encompasses the entire state of California as well as the Mexican portion of the CFP. Particular emphasis is placed on the rare plants of Southern California. Genera and families of particular diversity in the collection include Astragalus (Fabaceae), Penstemon (Plantaginaceae), Clarkia (Onagraceae) and the Polemoniaceae. The earliest collections have been stored since the late 1970s, and collection efforts are ongoing, with approximately 150 new accessions added each year. All collections of rare taxa are split into multiple seed lots, with a backup sample of each stored at the National Center for Genetic Resource Preservation (NCGRP), the United States federal germplasm collection.

A bias in past collection efforts

Environmental protection laws in the United States and the state of California require mitigation efforts when legally protected threatened and endangered (T&E) species are being disturbed or extirpated. These efforts often include seed banking as a component of the overall mitigation plan. Through agreements with the United States Department of Fish and Wildlife Service (USFWS) and the California Department of Fish and Wildlife (CDFW), seed banks are regularly utilized as ex situ storage facilities for T&E species. Largely due to legally mandated salvage and protection of T&E species, a substantial portion of these taxa are stored in ex situ germplasm collections, including the RSABG seed bank (Figure 2; Meyer et al., 2014). These seeds, some of which represent populations which have been extirpated from nature, comprise a genebank of immense value, but represent a limited subset of the overall CFP diversity.

While regulatory processes have resulted in a significant portion of rare taxa being banked, there are many rare taxa in California which lack legal T&E status, and thus are not required to be seed banked if they are impacted or destroyed during development. The California Rare Plant Rank (CRPR), a rarity index maintained by the CDFW and California Native Plant Society (CNPS), lists a total of 2,343 taxa of conservation concern (CNPS, 2014), while the combined number of plants with Federal and and/or State legal status is only 284. Of the rarest extant taxa (those that are classified as 1B by the CRPR), only 30 percent have been conserved in ex situ collections, in comparison to 71 percent of those with federal T&E status. The Global Strategy for Plant Conservation (GSPC) Target 8 sets a goal of securing “at least 75 percent of threatened plant species in ex situ collections, preferably in the country of origin, and at least 20 percent available for recovery and restoration programmes” (GSPC 2014). This target is well within reach for legally protected taxa in California, but remains far from realized for rare plants without legal status.

New initiatives for plant conservation

In the past year, a collaborative effort has been developed to reach ex situ conservation goals in California. This project, known as the California Plant Rescue, includes a variety of conservation organizations, botanic gardens and seed banks.

Still in the organizing stages, the California Plant Rescue is seeking to seed bank the entire flora of California and set up monitoring programs for rare taxa. This is a lofty goal, and as the project begins, the immediate focus is on building seed collections of rare and threatened plants which have yet to be seed banked. As part of this collaboration, the California Plant Rescue has examined data from seed collections both in and out of California to create a list of existing seed accessions for California rare plants, and to identify gaps in germplasm collections which need to be filled (Meyer et al., 2014). We hope that this proactive approach will allow us to strategically focus and achieve goals which have not been met with legally mandated germplasm salvage.

Also of great concern to the California Plant Rescue and the RSABG seed bank is the flora of Baja California, Mexico. The northwestern portion of the state is part of the CFP and shares some floristic features with southern California. Like its northern counterpart, the flora of this region contains many endemic species and is also declining due to development and land conversion. In collaboration with Mexican federal agencies and NGOs, the California Plant Rescue plans to add northwestern Baja California to its target seed collection area.

The California Floristic Province presents an exciting opportunity for both conservation and restoration of its unique biodiversity. While threats continue to loom in the region, work continues to conserve land and develop germplasm collections of the rarest botanical diversity. It is our hope that the California Plant Rescue collaboration will greatly accelerate progress in building ex situ collections of the unique plants of this region.

Acknowledgements:

I would like to thank Naomi Fraga and Nick Jensen, who coauthored a peer reviewed paper with me from which much of this article is adapted. I would also like to thank Abby Hird, Loraine Washburn and Naomi Fraga for reviewing an early draft of this article and providing useful suggestions.